Sizing composition for composite yarns and composite yarns coated with this composition

ABSTRACT

Composite yarn comprising an intimate mixture of glass filaments and thermoplastic filaments, wherein said composite yarn is coated with an aqueous sizing composition containing at least one additive in the form of a fatty acid ester; and the aqueous sizing composition per se.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sizing composition for compositeyarns and to composite yarns coated with this composition.

2. Discussion of the Background

Composite yarns (also called hybrid yarns) are yarns composed of organicfilaments and glass filaments and are used for the production ofcomposite products. These yarns are mainly obtained by combiningtogether glass filaments and thermoplastic filaments directly under thedie so as to obtain good mixing ("intimate" mixing) of glass filamentsand thermoplastic filaments. The processes for obtaining composite yarnsdirectly at the die are specially described in Patents EP-A-O 367 661(U.S. Pat. No. 5,011,523), EP-A-O 505 275 (U.S. Pat. No. 5,328,493),EP-A-O 505 274 (U.S. Pat. No. 5,316,561), WO 93/15893, EP-A-O 599 695and EP-A-O 616 055. Before combining together the glass filaments andthermoplastic filaments under the die, the glass filaments are coatedwith a sizing composition intended, especially, to protect the yarnsfrom abrasion. This sizing composition is usually an aqueous composition(it generally contains more than 90% by weight of water), the aqueouscompositions being easier to handle and conventionally suitable forcoating glass filaments (this type of composition especially having avery high wetting power with respect to glass filaments).

However, thermoplastics have little or no affinity with water and theirhydrophobic nature leads to a phenomenon of repulsion between the sizedglass filaments and the thermoplastic filaments. This phenomenon isaccentuated during the drying which is generally carried out oncomposite yarns in the case of use of an aqueous sizing composition (inparticular, drying enables the composite yarns to be used more easily inconversion processes, such as extrusion processes). The glass filamentsthen tend to group together as the water progressively evaporates, thethermoplastic filaments being ejected to the outside of the compositeyarn. Instead of obtaining the desired intimate mixing of glassfilaments and thermoplastic filaments within the composite yarns, asegregation of the thermoplastic filaments is therefore observed, withpartial or complete lack of cohesion of the hybrid yarn, thethermoplastic filaments in particular ending up without any protectionfrom the risks of abrasion or electrostatic phenomena.

The segregation of the thermoplastic filaments and their absence ofprotection from abrasion pose problems, in particular when using thecomposite yarns in textile applications, for example in weaving in whichthe yarns rub on feed rollers. In such cases, the composite yarns coatedwith aqueous size tend to break and to disrupt the running of thetextile machines. The poor mixing between the glass filaments andthermoplastic filaments, associated with the segregation resulting fromthe use of a conventional aqueous sizing composition, is moreoverobserved in composites obtained from composite yarns comprising the saidglass filaments and the said thermoplastic filaments, these compositesnot having a very satisfactory surface appearance.

SUMMARY OF THE INVENTION

The object of the present invention is to remedy the previouslymentioned problems. This object is achieved by using a suitable sizingcomposition in order to coat the glass filaments before they arecombined together with the thermoplastic filaments, this composition forcomposite yarns comprising a base mixture and at least one additive inthe form of a fatty acid ester.

By "base mixture" is meant, according to the invention, any aqueoussizing composition usually used for the coating of glass filaments underthe die, this composition usually being in the form of an aqueoussolution, an aqueous emulsion or an aqueous suspension. Examples of"base mixtures" will be given later.

The present invention also relates to the composite yarns which arecoated with the sizing composition according to the invention and areobtained directly under the die, these composite yarns having improvedproperties compared to composite yarns obtained under the die usingconventional sizes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sizing composition according to the invention meets the requirementsof sizing compositions which have to coat glass filaments as they arebeing drawn down at the die; it is homogeneous and stable, especially atthe die, and it withstands the shearing induced by the filaments passingthrough at high speed. In addition, the composition according to theinvention wets the surface of the glass filaments at high drawing speedswell and allows good lubrication of the glass filaments, thus protectingthem from abrasion.

The composition according to the invention furthermore has very goodwetting power, not only with respect to the glass filaments but alsowith respect to the thermoplastic filaments. The sizing compositiondeposited on the glass filaments can therefore migrate partly along thethermoplastic filaments after the two types of filament have come intocontact. The size is thus distributed uniformly over the entirecomposite yarn obtained, the glass filaments and thermoplastic filamentsbeing perfectly wetted by the composition.

The thermoplastic filaments within the composite yarns coated with thecomposition according to the invention are lubricated and protected fromabrasion and show little capacity for becoming electrostaticallycharged, like the glass filaments. Good mixing of the glass filamentsand thermoplastic filaments and cohesion of the said filaments are alsoobserved within the composite yarns.

The advantages of the composite yarns coated with the compositionaccording to the invention are manifold: such yarns are particularlysuited to being woven without the risk of breakages and the impregnationof such yarns by an organic material is improved. The compositesobtained from the composite yarns, optionally combined with anadditional organic material, have a highly satisfactory surfaceappearance, better than that of composites obtained in the same way butusing composite yarns coated with conventional sizes, the mechanicalproperties of composites obtained using the yarns according to theinvention being just as good as the mechanical properties of compositesobtained using conventional composite yarns.

The composition according to the invention may comprise, as basemixture, any conventional aqueous sizing composition, the base mixturebeing conventionally chosen by those skilled in the art from the knowncompositions, depending in particular on the type of thermoplasticfilaments which are combined with the glass filaments, on theapplication of the composite yarn coated with the composition and on theorganic materials which are to be combined with the said yarn.

In general, the base mixture of the composition according to theinvention comprises at least 85%, and preferably at least 90%, by weightof water and comprises at least one compound acting as a coupling agent.According to one embodiment of the invention, the base mixture thuscomprises at least one coupling agent, such as a silane, a titanate,etc., enabling the sizing composition to bond onto the glass. The basemixture may also comprise other coupling agents making it possible,after drying the yarns coated with the sizing composition, to improvethe bonding between glass and combined organic material and, inparticular, one or more "coupling co-agents" acting in a complementarymanner to that of the aforementioned coupling agent or agents andallowing, for example, the creation of interactions between the couplingagent or agents and the combined organic material. In particular, in thecase in which the composite yarns according to the invention consist ofglass filaments and polyolefin-type thermoplastic filaments, and in thecase in which they are intended to reinforce polyolefin materials, thebase mixture may comprise, in emulsion form, one or more polyolefins ofa kind similar to the polyolefins of which the thermoplastic filamentsand/or the material to be reinforced are composed, the polyolefins ofthe emulsion contributing to the coupling between glass and material tobe reinforced.

The base mixture of the composition according to the invention may alsocomprise one or more neutralizing agents and/or stabilizers, or anyother type of agent conventionally used in sizing compositions forcomposite yarns.

According to advantageous embodiments of the present invention, in thecase in which the composite yarns according to the invention comprisepolyolefin (more particularly polypropylene) filaments and in the casein which they are intended to reinforce a polyolefin (more particularlypolypropylene) material, the base mixture of the composition accordingto the invention coating the said yarns comprises at least onesilane-type, preferably aminosilane-type, coupling agent enabling thecomposition to bond onto the glass, at least one polyolefin(respectively polypropylene) coupling co-agent grafted by at least oneacid or acid anhydride, and preferably by at least one maleic anhydride,having a complementary role to that of the silane-type coupling agentand enabling the bonding between glass and polyolefin (respectivelypolypropylene) to be improved, and at least one neutralizing agent orstabilizer making it possible to neutralize, temporarily, and untildrying, the grafting functional groups of the polyolefin (respectivelypolypropylene) coupling agent or to stabilize the base mixture.

By way of example, the abovementioned silane may be aγ-aminopropyltriethoxysilane or anN-2-aminoethyl-γ-aminopropyltriethoxysilane and the neutralizing agentor stabilizer may be an inorganic or organic base (sodium hydroxide,potassium hydroxide, aqueous ammonia or a primary, secondary or tertiaryamine, etc.).

The sizing composition according to the invention comprises, in additionto the base mixture, at least one additive in the form of a fatty acidester. Preferably, this additive is an alkoxylated fatty acid ester andadvantageously it comprises one or more hydroxyl functional groups. Byway of example, this additive may be an ethoxylated fatty acid esterwith hydroxyl functional groups.

The amount of additive(s) in the form of fatty acid ester(s) in thecomposition is generally from 1 to 15% by weight and advantageously from1 to 10% by weight with respect to the base mixture. Preferably, it isfrom 1 to 8% by weight and particularly preferably it is from 1 to 6% byweight with respect to the base mixture. This or these additives may beadded during the compounding of the base mixture or they may be addedmore simply to the already-compounded base mixture.

It should be noted that the neutralizing agent (or stabilizer) mentionedpreviously may also serve to neutralize the alcohol functional groups ofthe added fatty acid ester, in particular to prevent the reaction of thealcohol functional groups of the ester with the amine functional groupsof the silane when the silane used is an aminosilane. In this case, whenthe base mixture used comprises a neutralizing agent (or stabilizer),the quantity by weight of neutralizing agent in the compositionaccording to the invention is optionally increased with respect to theinitial quantity of neutralizing agent in the base mixture so as toallow both the desired neutralization within the base mixture (forexample the neutralization of the polyolefin coupling agent in thepreviously mentioned embodiment) and that of the fatty acid ester.

The fatty acid ester may also be neutralized by a neutralizing agent (orstabilizer) which is different from that used as the case may be in thebase mixture, this additional neutralizing agent being added during thecompounding of the composition according to the invention.

According to preferred embodiments of the present invention, in whichthe composite yarns comprise polypropylene (and more generallypolyolefin) filaments and/or in which the composite yarns are intendedto reinforce a polypropylene (respectively polyolefin) material, thecomposition according to the invention coating the said yarns comprisesa base mixture consisting of 0.05 to 3% by weight, and advantageously0.1 to 1.5% by weight, of a silane-type coupling agent, 1 to 10% byweight of a polypropylene (respectively polyolefin) coupling agentgrafted by at least one acid or anhydride and 0.1 to 5%, andadvantageously 0.2 to 1.5%, by weight of a neutralizing agent orstabilizer, the composition comprising, in addition to this basemixture, a fatty acid ester added in an amount from 1 to 10%,advantageously from 1 to 6%, by weight with respect to the base mixtureand, optionally, an additional neutralizing agent which may or may notbe identical to that already present in the base mixture and in aquantity sufficient to neutralize the fatty acid ester.

The composite yarns according to the invention are obtained inparticular according to the following process: streams of molten glassare drawn into the form of fans of continuous filaments from theorifices of one or more dies and the filaments are coated with thesizing composition according to the invention (that is to say of thecomposition comprising a base mixture to which a fatty acid ester hasbeen added) with the aid of one or more coating devices, such as sizingrollers, while simultaneously a thermoplastic organic material isextruded and entrained, the paths followed by the glass filaments and bythe thermoplastic filaments converging on each other before the saidfilaments are combined together into a mechanically entrained compositeyarn.

The composite yarns according to the invention may also be obtainedaccording to any one of the processes described in Patents EP-A-O 367661, EP-A-O 505 275, EP-A-O 505 274, WO 93/15893, EP-A-O 599 695 andEP-A-O 616 055.

By extension, by "composite yarns coated with a sizing composition" aremeant "yarns composed of organic filaments and of glass filaments whichhave been coated with a sizing composition", that is to say not only thecomposition-coated yarns obtained after combining together the organicfilaments and the sized glass filaments but also these same yarns afterdrying and/or after other Treatments which are intended to removecertain components from the composition (especially water) and/or topolymerize certain components of the composition.

The composite yarns according to the invention may be collected in theform of continuous yarns or tapes, or may be cut either directly underthe die by a device serving to entrain them mechanically or subsequentlyfrom the wound packages of continuous yarns obtained, etc. Thus, thepresentation of the composite yarns varies depending on theirapplication.

The quantity of size deposited on the composite yarns according to theinvention is about 0.2 to 5% by weight, and preferably 0.2 to 3% byweight, with respect to the yarns. These yarns are subjected to dryingbefore they are combined at all with an organic material to bereinforced.

As indicated previously, the composite yarns according to the inventionare particularly suited to weaving as well as to the production ofcomposites, whether or not they are combined with an additional organicmaterial. The composites may in particular be obtained by supplying anextruder using the composite yarns according to the invention, asdescribed in Patent Application EP-A-O 541 441.

The sizing composition for composite yarns and the composite yarnsaccording to the invention will be more clearly understood through thefollowing examples illustrated by the figures, such that:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows an electron microscope photograph of a cross-section of aconventional composite yarn and

FIG. 1b shows a slightly simplified diagram of the said photograph;

FIG. 2a shows an electron microscope photograph of a cross-section of acomposite yarn according to the invention and

FIG. 2b shows a slightly simplified diagram of the said photograph.

REFERENCE EXAMPLE

800 glass filaments of 17 μm in diameter, obtained by drawing moltenE-glass from a die, coated using a graphite sizing roller with a sizingcomposition ordinarily used for composite yarns consisting ofpolypropylene filaments and glass filaments, are combined with 800polypropylene filaments of 23 μm in diameter, these two types offilament being combined together into one yarn (or "roving") which iswound in the form of a straight-sided wound package.

The polypropylene filaments are formed by extruding a product, marketedunder the reference "VM 6100 K" by Shell, to which has been added acoupling agent, marketed under the reference "Polybond 3002" by UniroyalChemical, in a proportion of 4% by weight with respect to thepolypropylene.

The sizing composition deposited on the glass filaments comprisesapproximately 1% by weight of an aminosilane, approximately 0.5% byweight of a neutralizing agent of the amine type, approximately 13% byweight of an emulsion of polypropylene grafted by a maleic anhydride,this emulsion containing approximately 55% of water. The total quantityof water in this size is approximately 93%.

On the filaments, glass or polypropylene, of which the composite yarn iscomposed, the angle of contact with the size used is measured on amono-filament with a Khan balance. The results are given in the appendedTable I.

Friction tests are also carried out on the hybrid yarn obtained, bypassing the yarn over 3 steel bars 8 mm in diameter at a speed of 100m/min and at an input tension F₁ of the order of 120 cN. The outputtension F₂ of the yarn is measured and the coefficient of friction μ isdetermined from the formula: F₂ --F₁ e.sup.(μα), α being the sum of theangles of contact of the yarn on the bars (in this case about 370°). Theresults are given in the appended Table II.

A Rotschild test on a Rotschild R 4021 electrostatic voltmeter is alsocarried out on the yarn at 60% relative humidity and at 20° C., in orderto evaluate the capacity of the yarn to be electrostatically charged.The yarn is charged between 2 electrodes (150 V) and the measured halfdischarge times are given in the appended Table II.

The mechanical properties of the composites, obtained by injectionmoulding granulated fibres 12 mm in length produced from the hybrid yarnpreviously obtained, are also measured. The tensile and flexuralstrengths, and the unnotched Charpy and notched Izod impact strengthsare measured under the conditions defined respectively by the StandardsISO R 527, ISO R 178, ISO R 179 and ISO R 180 and are given in theappended Table III.

The composite yarn obtained is moreover passed through a jacketingnozzle so as to hold the yarn with a view to cutting it. The jacketedyarn is then immersed in a thermosetting resin and placed in a vacum inorder to remove the bubbles before cutting and polishing operations forthe purpose of taking an electron microscope photograph of thecross-section of the yarn.

FIG. 1a illustrating the photograph obtained shows the distribution ofthe various filaments within the composite yarn in the present example.According to FIG. 1b, which constitutes a simplified diagram of thecross-section shown in FIG. 1a and bearing the reference numbers (FIG.1a not bearing the reference numbers for the sake of clarity), thecomposite yarn comprises glass filaments 1 and polypropylene filaments2, the yarn being surrounded by a jacket 3 and having, at certainplaces, traces of a thermosetting impregnation resin 4 (the jacket andthe resin being only for the requirements of the photography). From thephotograph and the representation of it, a major segregation of thethermoplastic filaments within the reference composite yarn is observed.

EXAMPLE 1

The same procedure is carried out as in the reference example, with theaddition to the sizing composition of 3% by weight of an ethoxylatedfatty acid ester with hydroxyl groups, this product being marketed underthe reference "Ensital PRF 416" by Sidobre Sinova.

The results of the various tests are given respectively in the appendedTables I, II and III.

FIG. 2a illustrates the photograph, taken as in the reference example,of the cross-section of the yarn obtained. Quite homogeneous mixing("intimate" mixing) is observed between the glass filaments 11(corresponding to the white parts in FIGS. 2a and 2b) and thethermoplastic filaments 12 (black points) within the yarn. This yarn issurrounded by a jacket 13 for the requirements of the photography, as inthe reference example.

EXAMPLE 2

The same procedure is carried out as in Example 1, adding 6% by weightof Ensital PRF 416 to the sizing composition.

The results of the various tests are given in the appended Tables II andIII.

From Table I, it may be observed that the conventional sizingcomposition used in the reference example wets the glass very well andthe polypropylene very poorly. It therefore tends to remain on the glassfilaments. As regards the sizing compositions according to the inventionwhich are used in Examples 1 and 2, they wet the glass very well and thepolypropylene very well. There is therefore transfer of part of thecomposition deposited on the glass filaments to the polypropylenefilaments. This transfer takes place by contact between glass filamentsand polypropylene filaments.

From Table II, it may also be observed that the use of a sizingcomposition according to the invention results in a reduction in thecoefficient of friction, depending on the concentration of ethoxylatedfatty acid ester in the composition. In addition, when the yarnaccording to the reference example is used as the warp yarn on a loom inorder to manufacture a woven fabric, deposits of fluff are formed andbuild up on the healds of the loom and result in a stoppage of the loomevery 20 to 50 meters of woven yarn. In contrast, the yarns according toExamples 1 and 2 give rise to no deposition and an entire warp ofseveral thousands to tens of thousands of meters of these yarns may beused without the loom stopping.

A very significant reduction may also be observed in the capacity forthe yarns according to Examples 1 and 2 to be electrostatically charged,compared to the yarn according to the reference example.

Finally, it may be observed that the mechanical properties of thecomposites obtained from the yarns according to Examples 1 and 2 arejust as good as the mechanical properties of the composites obtainedfrom the yarns according to the reference example. The same observationmay be made irrespective of the method of production of the compositesfrom the composite yarns; thus, for composites produced from sheets offabrics woven from composite yarns, the mechanical properties of thecomposites produced from the yarns according to the invention are atleast as good as the mechanical properties of the composites producedfrom the conventional composite yarns.

The sizing composition according to the invention is suitable for anytype of composite yarn: glass/polyamide, glass/polyester, etc., and thecomposite yarns coated with size according to the invention may servefor textile applications or may be used directly in order to producecomposites by moulding, injection moulding, etc.

                  TABLE I                                                         ______________________________________                                        Reference Example   Example 1                                                 Glass        Polypropylene                                                                            Glass     Polypropylene                               filaments        filaments                                                                              filaments                                                                                  filaments                              ______________________________________                                        Angle of                                                                             0° 45° 14°                                                                            20°                                contact                                                                       ______________________________________                                    

                  TABLE II                                                        ______________________________________                                                    Coefficient of                                                                friction        Half discharge time(s)                            ______________________________________                                        Reference Example                                                                           0.44       40 to 60                                             Example 1                                     9                               Example 2                                     9                               ______________________________________                                    

                  TABLE III                                                       ______________________________________                                                               Unnotched  Notched Izod                                        Tensile                                                                                Flexural                                                                                  Charpy impact                                                                        impact                                            strength                                                                              strength                                                                                   strength                                                                                  strength                                     (MPa)     (MPa)                                                                                       (kJ/m.sup.2)                                                                            (J/m)                               ______________________________________                                        Reference Ex.                                                                           139.3   214      71       66                                        Example 1       138                                                                                     210                                                                                                70                             Example 2       137                                                                                     215.5                                                                                 70.5                                                                                      63                              ______________________________________                                    

We claim:
 1. Composite yarn comprising an intimate mixture of glassfilaments and thermoplastic filaments, wherein said composite yarn iscoated with an aqueous sizing composition comprising a base mixture andat least one additive in the form of an alkoxylated fatty acid estercomprising one or more hydroxyl functional groups.
 2. Composite yarnaccording to claim 1, wherein the amount of additive(s) in the form offatty acid ester(s) in the sizing composition is between 1 and 15% byweight with respect to the base mixture.
 3. Composite yarn according toclaim 1, wherein the base mixture of the sizing composition comprises atleast 85% by weight of water and at least one coupling agent. 4.Composite yarn according to claim 1, wherein the sizing compositioncomprises at least one polyolefin.
 5. Composite yarn according to claim4, wherein the sizing composition comprises at least one polypropylenegrafted by at least one acid or acid anhydride.
 6. Composite yarnaccording to claim 1, wherein the sizing composition comprises at leastone neutralizing agent or stabilizer.
 7. Composite yarn according toclaim 1, wherein the composite yarn has a loss on ignition of between0.2 and 5% by weight.
 8. Composite yarn according to claim 1, whereinthe amount of additive(s) in the form of fatty acid ester(s) in thesizing composition is a segregation-reducing effective amount. 9.Composite based on organic material(s) and on glass, wherein thecomposite comprises, at least in part, composite yarns according toclaim
 1. 10. Aqueous sizing composition for composite yarns, containingat least one additive in the form of an alkoxylated fatty acid estercomprising one or more hydroxyl functional groups.
 11. Composite yarncomprising an intimate mixture of glass filaments and thermoplasticfilaments, wherein said composite yarn is coated with an aqueous sizingcomposition containing at least one additive in the form of a fatty acidester, wherein the fatty acid ester is an alkoxylated fatty acid estercomprising one or more hydroxyl functional groups.
 12. Composite yarnaccording to claim 11, wherein the amount of additive(s) in the form offatty acid ester(s) in the sizing composition is a segregation-reducingeffective amount.
 13. Composite yarn comprising an intimate mixture ofglass filament and thermoplastic filaments, wherein said composite yarnis obtained by coating the glass filaments with an aqueous sizingcomposition containing at least one additive in the form of analkoxylated fatty acid ester comprising one or more hydroxyl functionalgroups to form coated glass filaments, and then intimately mixing saidcoated glass filaments with said thermoplastic filaments, wherein saidsizing composition is distributed over the composite yarn.
 14. Compositeyarn according to claim 13, wherein the amount of additive(s) in theform of fatty acid ester(s) in the sizing composition is asegregation-reducing effective amount.